1. Field of the Invention
The present invention relates generally to charts utilized to display different colors in a systematic manner. More particularly, it relates to a new coordinated color chart system and to a method for producing the same whereby each color chart contains a plurality of coordinated, distinct colors obtained by varying the amounts of all of three colorants, it being possible with the invention to develop color charts so that they are arrayed on a linear scale generally corresponding to a linear gray scale.
2. Description of the Prior Art
Human beings have had a long fascination with the colors seen by their eyes, and many efforts have been undertaken to analyze and classify the many perceivable variations of color. These efforts have taken on a special importance in our age, when we have available to us the techniques and skills to produce color television, color photography, and color reproduction through printing, dyeing and other processes.
The many processes and techniques utilizing color in today's world demand that there be a system for classifying colors so that they can be readily compared, and to help those engaged in producing goods where color is a factor so that there is some common base for defining, selecting and reproducing different colors. In the printing field, for example, those producing original maps and pictures utilizing colors and which are intended for reproduction need to correlate their color selections with what can be reproduced by the available printing processes, if faithful reproductions are to be obtained. Moreover, selected colors should bear a known relationship to each other, so that desired contrasts and blends of colors are easily achievable.
Over the past several decades there have been many efforts made to rationalize the identification, classification and comparison of colors. Much basic work that is still commonly accepted was done by Munsell, one of the early results of which was a color chart that is the subject of U.S. Pat. No. 1,617,024. The Munsell system of color notation identifies color in terms of three characteristics, hue, value and chroma, and in the Munsell chart the three characteristics are arranged into orderly scales of equal visual steps. The Munsell system is useful for many purposes, but is not designed to solve in an everyday practical way the joint needs of those who must choose colors for use, and those who are then responsible for reproducing those colors through a printing or like process. Specifically, the Munsell system does not make it easy to select colors that are correlated and easily reproducible.
There have been other systems and devices invented for identifying and comparing colors, such as those which are the subject of U.S. Pats. Nos. 1,703,449, 2,409,285, 2,128,676, and 1,480,486. Again, while the inventions of these patents are useful, they do not offer the capability of identifying and readily comparing large numbers of colors to the satisfaction of increasingly sophisticated needs.
In more recent years the concept has developed of utilizing a color cube to identify and analyze different colors. In a color cube different primary colorants are displayed along the edges of a cube. Each face of the cube is then developed to look much like a checkerboard, except that each square on the face represents a unique combination of the primary colors displayed along the respective cube edges.
Each face of a color cube thus constitutes a color chart. In addition, vertical and horizontal planes are commonly passed through the cube to produce yet further color charts, examples of the use of the color cube concept being shown by U.S. Pat. Nos. 3,474,546 and 3,751,829.
Because the present invention also makes use of the color cube concept, it would be useful to describe a typical color cube system of the kind now in use. Assuming that the three primary colors of yellow, magenta and cyan are to be employed, such will be arrayed along three mutually perpendicular and intersecting edges of a cube, with say cyan running vertically, and magenta and yellow running at right angles to each other at the top of the cube in opposite directions from the vertical edge carrying cyan.
The cube corner where the three colorant-carrying edges merge is taken as the base point, and the amount of intensity of each color will vary from a minimum at this intersection base corner to a maximum at the opposite end of the edge. The color variation will normally be uniform along each edge, and the edge will be marked off in a scale of, say, percent value of the screen used in printing the color. The faces of the cube along which the three primary colorant-carrying edges border are then developed in the manner of a checkerboard, using the marked scale as a guide.
The result will be that each square on each face of the cube will have a specific amount of each of the two primary colorants present, the combination being unique for each square, whereby each square represents a unique color. The value of the third colorant will be uniform on each face. Each of the cube faces thus constitutes a color chart, whereon the colors are arranged rationally and in an orderly manner, but with a variation of only two of the three colorants.
But the number of color charts derivable from the color cube is not limited to the faces thereof. Rather, additional charts are derived conventionally by passing vertical and/or horizontal planes through the cube, at selected points along the color value scales. The result is a large numer of color charts, which can be arranged in several ways, and which in total present a very large number of distinct colors, the constituent primary colorants and the amount thereof required for each of the distinct colors being known.
More specifically, for each vertical or horizontal plane it is evident that the amount of one colorant will be constant, while the other two colorants will vary. Thus, for each selected value of a first colorant, all the possible combinations of colors derivable by varying the selected values of the other two colorants can be displayed on a checkerboard-like chart.
A set of charts derived conventionally from a color cube in this manner will offer a wide selection of unique colors to the person seeking specific colors for use on a map, picture or the like, and to a printer who must reproduce the colors of an original work. However, the set of charts is not easy to use, and often fails to give the results desired. The reasons are several.
First of all, it is evident that on each chart one of the colorant values will remain constant, while the values of the other two colorants are varied. This makes it difficult to find and compare colors where all three colorants are varied. Considerable movement around of the charts is required, and even when the proper charts are side-by-side, comparison of colors deep within the charts is difficult.
An extension of this problem occurs when it is desired to select complementary, but contrasting, colors. Again, because only two colorants are actually varied on a given chart, it is difficult to select contrasts, and to determine the compatibility of a selected color on one chart with a selected color on a second or other charts.
Other problems associated with the charts derived conventionally from a color cube by using such horizontal and/or vertical planes are the handling and logical filing of the charts, and the difficulty to the printer in selecting a matching color for an object to be reproduced. This last problem often results in a printer having to resort to trial and error to match a color, a process that often is lengthy and always wasteful of valuable printing resources.
There is thus need for a new system of color charts wherein the colors are arranged logically and rationally so that contrasting colors can be readily selected, complementary colors readily determined, and the proper mixture of inks for color reproduction easily analyzed. Further, there is need for a system of color charts wherein on each chart the values of all the three primary colorants are varied, not just two, so that color relationships can be more readily observed. The present invention is intended to satisfy these needs, and as such constitutes a significant advance in the color art.